•R factor for Coupled Composite Plate Shear Walls-Concrete Filled were determined.•These walls benefit from the added energy dissipation by coupling beams.•The results presented show that R factor of ...8 is adequate for design of these walls.
ASCE7–16 (2016) 4 defines three seismic performance factors to approximately predict the inelastic response of a seismic resisting system. These factors are the response modification factor, R; deflection amplification factor, Cd; and the system over-strength factor, Ωo. The research presented here was conducted, using FEMA P695 methodology, to determine the value of the above factors for a special seismic-force resisting system defined as Coupled Composite Plate Shear Walls-Concrete Filled (CC-PSW/CF). The ASCE 7–16 (2016) 4 and AISC 341–16 (2016) seismic provisions provide specific requirements for the use of planar composite steel plate shear walls in seismic regions. However, the ASCE-7–16 standard does not differentiate between coupled and non-coupled walls. Coupled walls can benefit from the added energy dissipation provided by their coupling beams and are accordingly expected to exhibit better seismic hysteretic behavior than uncoupled walls. Therefore, coupled walls systems should arguably have a higher response modification factor value. In this paper, the FEMA P695 approach taken for determining the seismic parameters of CC-PSW/CF is presented. To enhance confidence in the results, the Incremental Dynamic Analyses needed as part of the P695 procedure were conducted in parallel using two different non-linear hysteretic models. Complementary studies were also conducted to investigate the sensitivity of results to assumptions related to damping and yielding models. Results show that values R = 8, Cd = 5.5, and Ωo = 2.5 would be appropriate for CC-PSW/CF.
•FEM and experimental results agree well.•Damage mechanism of SBJs was investigated.•Effects of laminate stacking sequences, metal and adhesive properties were analyzed.
Composite-to-metal 2D (two ...dimensional) scarf bonded joint (SBJ) specimens with 4scarf angles were tested to study their tensile behaviors. Based on the experimental results, progressive damage finite element models (FEM) were established in ABAQUS/Standard, and the effects of three variables: the metal material, composite stacking sequence and adhesive properties, with respect to the joint tensile properties were investigated. The results show that the metal plasticity and scarf angle can affect the tensile plastic behavior of the joint. Compared with Q235 (steel), 7075-T6 (aluminium) and 30CrMnSiNi2A (steel) plates, TC4 (titanium) plate makes the joint possess higher tensile strength. Changing the composite plate (laminate) stacking sequences can result in the variation of plastic behavior and failure location of the joints. The adhesive properties have significant effects on the joint plastic behavior and ultimate loads.
The aim of this laboratory study was to evaluate the monomer leaching and degree of conversion (DC) from experimental bioactive resin composites (RBCs) and to do comparison with commercial bulkfill ...and packable resin composites. Experimental dimethacrylatebased resin composites were reinforced with silanated nano-hydroxyapatite (30 and 45 wt%). The ion leaching and DC of these resin composites were compared and contrasted with SDR™ and Filtek P60™ by using the high performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR), respectively. A significant difference was found in elution of monomer between the resin composites. SDR™ showed significantly high monomer elution and structural changes compared to other resin composites. The DC of bioactive RBCs showed the highest conversion rate after polymerization. Resin composite with nano-hydroxyapatite with the presence of a bioactive component might provide biomimetic approach for the material. Moreover, a low concentration of nanohydroxyapatite nano-fillers have shown better properties than micro-fillers based resin composites.
Hydrothermal aging is a matter of considerable concern for natural fiber-reinforced polymers; it can alter dimensional stability and induce microcracks and macro strain on the composite structure. ...This study applied a sorption kinetic model and examined the effects of water on the damping factor of sisal mat-reinforced polyester composites. The experimental data were fitted well using a Boltzmann sigmoid function, suggesting a promising first step toward kinetic water sorption modeling. Additionally, a damping test was carried out using the impulse excitation technique, highlighting the composite material's dynamic response under varying water absorption conditions. The result showed that damping exhibited sensitivity to water absorption, increasing significantly during the first 24 h of immersion in water, then remained steady over time, inferring a critical time interval. An empirical model proved satisfactory with the correlation coefficient for sorption rates and damping of sisal mat polymeric composites.
Improving thermal stability of high-performance polymer-based nanocomposite films for electrical energy storage is essential to meet ever-increasing demands for the electrical industry, especially at ...harsh environment applications. Here, the polyetherimide (PEI)-based composites films are prepared via grafting method in the presence of SrTiO3 (ST) nanofillers to substantially improved capacitive performances at elevated temperature. The composites films with the optimized filler compositions show a high discharged energy density of 6.76 J/cm3 under 600 MV/m at room temperature. Meantime, excellent high-temperature discharged energy density of 6.6 J/cm3 at 100 °C for the composites films is also achieved, which is superior to most of the previously reported. The simulations further demonstrate that the ST nanoparticles embedded into the composites films could effectively improve heat dissipation in comparison with pristine PEI matrix, resulting in enhancement high-temperature energy storage capabilities. This work gives considerable promise for high energy density polymer-based nanocomposite films capacitors under harsh environments.
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•SrTiO3 nanoparticles/polyetherimide nanocomposite film are designed and prepared by grafting method.•The composite film obtains excellent high-temperature energy storage performance.•An excellent high-temperature discharged energy density of 6.6 J/cm3 at 100 °C is achieved.
•Deep autoencoder-based fatigue damage diagnosis technique for composite structures.•Non-destructive fatigue damage evaluation using ultrasonic Lamb waves.•Fatigue damage detection by analyzing ...statistical patterns in Lamb wave signals.•Automated composite fatigue damage classification through feature learning approach.
This paper presents the development of a robust automatic damage diagnosis technique that uses ultrasonic Lamb waves and a deep autoencoder (DAE) to detect and classify fatigue damage in composite structures. Piezoelectric (PZT) transducers are installed on carbon fiber reinforced polymer (CFRP) composite plate specimens to interrogate structural integrity under uniaxial fatigue loading. Fatigue damage evolution from matrix cracking to delamination is monitored by periodically acquiring the ultrasonic wave response. A deep autoencoder (DAE) model is adopted for effective tracking of ultrasonic response variations and for diagnosing fatigue damage in the composite specimens. The ultrasonic signals collected from pristine specimens are processed and used for training the DAE model. To improve the accuracy and sensitivity of the damage diagnosis, the architecture and hyperparameters of the DAE model are optimized, and a statistical detection baseline is defined to capture damage indicators. The ultrasonic signals obtained after applying additional fatigue cycles are introduced into the trained DAE model to validate the damage detection and classification capabilities. The damage sensitive features automatically extracted from the bottleneck layer of the DAE model are used to classify the fatigue damage mode. Singular value decomposition (SVD) is used to further reduce feature dimensionality. The patterns in the reduced features are then analyzed using a density-based spatial clustering of applications with noise (DBSCAN) algorithm. The results show that the proposed technique can accurately detect and classify the fatigue damage in composite structures, while removing the need for manual or signal processing-based damage sensitive feature extraction from ultrasonic signals for damage diagnosis.
The stability of the sandwich composite structures formed by leaving coal pillar, roof rock and floor rock (RCF) is of great significance to safe production of coal mines. The failure of coal and ...rock is actually a state instability phenomenon driven by energy. In order to explore energy characteristics of RCF sandwich composite structures, uniaxial compression tests with different coal thicknesses were performed by numerical simulation tests. The test results show that the strength and elastic modulus of RCF sandwich composite structures are lower than roof or floor rock single body and higher than coal single body when coal are taken different thicknesses. Main failure modes of coal and rock single bodies are cleavage, while main failure modes of RCF sandwich composite samples are shear. The peak strength and elastic modulus of RCF composite samples decrease with the increasing of coal thicknesses. The total input energy U, releasable elastic strain energy Ue and dissipative energy Ud all decrease first and then increase with increase of coal thickness. And a new damage constitutive model was established based on the dissipative energy and total input energy at peak strength, and damage evolution curve and equation of RCF composite samples were obtained. The study laid a foundation for the disaster evolution process of the RCF sandwich composite structures and mechanism of disaster time effect.
Carbon–carbon, carbon–silicon carbide, and silicon carbide–silicon carbide composites were vacuum brazed to Ti and Hastealloy X using Ni-base metallic glass braze foils (MBF-20 and MBF-30). Scanning ...electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) of the joints showed that compositional changes due to substrate dissolution led to secondary-phase precipitation which aided interfacial bonding although inter-laminar shear failure occurred within some composites. Residual thermal stresses in the joint led to hardness gradients; however, stress accommodation by the brazes prevented interfacial cracking. The peak Knoop microhardness in the joints was as high as 1165–1294
KHN.
Carbon-encapsulation is an effective strategy to inhibit the volume expansion and enhance the cycle stability of silicon anode in the lithium-ion battery. However, it is still a big challenge to ...prepare carbon/silicon composite materials with excellent flexibility using a simple and high-efficient method. Herein, a flexible carbon-based composite membrane embedded with nano-silicon particles and graphene is successfully developed via simple precursor preparation and carbonization processes. The obtained carbon-based composite membrane possesses a porous 3D network structure, which can provide buffer space to alleviate the volume expansion of nano-silicon. Due to the unique architecture, the carbon-based composite membrane presents a high reversible capacity of 1135.7 mA h g−1 and an effective utilization rate of nano-silicon up to 92.6%. After 100 cycles, the reversible capacity is still maintained at 897.6 mA h g−1 with a capacity retention rate of 74.2%. Furthermore, after 100 cycles, almost no capacity loss is detected, and the Coulombic efficiency is close to 100%, demonstrating excellent reversibility and robust stability. In summary, this research provides a simple and high-efficiency strategy for the preparation of flexible carbon/silicon composite anodes for lithium-ion batteries.
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••A simple crossover strategy combined with NIPS technique and carbon materials was explored for flexible composite anode.•The obtained carbon-based composite membrane exhibited a developed 3D network structure with Si embedded in the matrix.•The 3D network structure provided a favorable buffer space for alleviating the volume expansion of Si.•The hybrids exhibited excellent flexibility, free-standing, and structural integrity before and after 200 cycles.•The unique design endowed a reversible capacity of 1135.7 mAh g−1 and the effective utilization rate of Si was up to 92.6%.
Additive manufacturing of fiber reinforced composites is of great interest in various industrial applications. In this study, an innovative extruder is designed and manufactured for fused deposition ...modeling (FDM) 3D printers in order to produce continuous fiber reinforced thermoplastic (CFRT) composites. There are some challenges along this way such as making tension in fiber, fiber surface preparation, printing temperature and feed rate to produce a composite part with good quality. These challenges are discussed in detail. The main advantage of this extruder is that it can be mounted on the available FDM 3D printers and consequently there is no need to design a new chassis. In order to assess the quality of products, standard tensile and three-point bending specimens made of pure poly lactic acid (PLA) and carbon fiber reinforced PLA are printed and tested under quasi-static loading. Experimental results show significant improvements of tensile and bending properties of PLA. Morphological analysis is also conducted to study the bonding between the carbon fiber and PLA.
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